As the performance requirements of both military and commercial aircraft increases, conventional control technologies cannot relieve the pilot from higher mental and manual control activity. As such, today's high performance aircraft as well as some transport aircraft use sidesticks, center sticks, yokes, joysticks and control columns. As used herein, these devices will be generically referred to either as “control columns” or “control sticks,” with these terms being generally synonymous in a generic sense.
The commercial and military aircraft industry is under pressure from both government and private consumer groups to build aircraft that is both safe and economical. Safety standards are imposed on the aircraft industry such that a safe and reliable experience is had for customers. Also, of importance to the aircraft industry is to build aircraft that present an economic solution to a customer's needs. A large factor that addresses economic concerns is the overall weight of an aircraft. A lighter aircraft will generally be cheaper to operate because generally the aircraft (within its flight class) will require less fuel to operate, among other reasons.
The tactile feel of the control sticks of an aircraft are an important safety aspect. The pilot needs to have tactile feedback in order to tell certain operating conditions for the engine(s) and various control systems present on modern aircraft.
One such tactile feel are detents. Typically, the detent feel provided for in the control sticks is created from a mechanical detent structure that will indicate to the person actuating the control stick that the aircraft is now in some specific mode or range of operation. However, mechanical systems are not ideal because they are both complex and heavy. Furthermore, a mechanical detent structure does not allow for the feel of the detent to be easily changed.
Therefore, electrical systems were created to reduce the complexity and weight of the previous mechanical system and allow for the ability to more easily alter the feel of the detent. Initially, analog electronic control systems were used to provide the control signals for a simple motor that would provide the detent feel. However, these analog systems were difficult to control in that they experienced a very low tolerance for component variability and would drift in operation range over time of operation and temperature during operation. To remedy this issue digital systems were implemented.
The digital systems typically use force sensors to sense the torque the operator applies to the control stick. By sensing the force applied to the control stick the digital system can determine how to properly simulate the mechanical detent feel. However, having to either sense or derive force can be a complex process in and of itself
Therefore, there is a need for a safe and cost effective simulated detent feel solution that eliminates the heavy and complex mechanical solution and the overly complex digital force sensing solution. Embodiments of the present invention provide such a solution. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.